1. Field of the Invention
The present invention relates to expanding tubulars in a well and more particularly, to methods and tools utilizing technology directed towards downhole expansion of tubulars.
2. Background of the Related Art
There are many types of operations that must be performed at some depth in a well and various tools and methods have been developed to perform these downhole operations. Downhole tools for example, are available with means for setting after being placed at some depth in a well. The tools are actuated in order to fix or set them in place in the well. In some cases, setting involves the setting of a slip to secure the position of the tool against the casing walls. For example, with casing liner, one string of casing is hung in the well at the end of a previous string and the liner must be set at the appropriate depth by actuating slips against the inner wall of the existing casing. In another example, a packer used to isolate an annular area between two tubular members, is set at a particular depth in a well prior to expanding its surfaces against the inner tube and the outer tube walls.
There are numerous known ways to set downhole tools. Typically, pressure build up inside or outside the tool is required. In some prior art tools, that pressure is typically communicated through a wall of the tool into a sealed chamber. An actuating piston forms part of the sealed chamber such that the cavity will grow or shrink in volume as the piston moves responsive to the increase or decrease of hydraulic pressure within the tool. These variable-volume cavities outside the wall of the tool are sealed off with eleastomeric O-rings or similar seals. The seals are subject to wear from contamination in wellbore fluids, stroking back and forth in normal operation, and/or temperature or chemical effects from the wellbore fluids. The biggest concern about seal wear is that an open channel could be created through the lateral port in the wall of the tool from inside to outside of the tool, thus upsetting well operations and costing critically expensive downtime for the well operator.
A more recent advance, described in U.S. Pat. No. 5,560,426 employs the principles of pressure differential but without fluid communication throughout he wall of the tool. Instead, the applied pressure differential creates a stress which allows the wall of the tool to flex and fracture a locking ring on the outside surface of the tool. When the ring fractures, a piston moves in reaction to the pressure differential and a spring loaded slip is driven onto a cone, thereby setting the tool in the well. While this technology is an improvement over those requiring an aperture in the tool wall, the structure and mechanical operations required are complicated and subject to failure. For example, in the apparatus described in U.S. Pat. No. 5,560,426, an atmospheric chamber is formed on the inside of the tool body as well as the outside. To begin the tool setting sequence, the outer chamber must be opened to the pressure of the well. Opening the outer chamber is performed by dropping a ball into a seat formed at the top of the chamber and then increasing pressure inside of the tubing and body until the ball, seat and chamber are blown down into the well bore. Assuming that the interior chamber is successfully opened to well pressure, the design also requires a flexing of the tool wall in order to fracture a frangible locking ring. The required flexing that must take place in the wall is difficult to calculate and predict when designing the tool and the locking ring.
Other problems associated with current downhole tools are related to space. A liner hanger with its slips and cones necessarily requires a certain amount of space as it is run-into the well. This space requirement makes it difficult to insert a liner hanger through previously installed tools like mechanical packers because the inside diameter of the previously installed tool is reduced. Space problems also arise after a slip and cone tool is set in a well because adequate clearance must be available for the subsequent flow of liquids like cement through the annular area between the tubulars.
Technology is emerging for selectively expanding the diameter of tubing or casing in a well. FIG. 1 depicts an expansion apparatus 100 which can be lowered into a well to a predetermined location and can subsequently be used to expand the diameter of the tubular member. The apparatus 100 comprises a body having two spaced-apart, double conical portions 102a, b with rollers 105 mounted therebetween. The rollers 105 may be urged outwards by application of fluid pressure to the body interior via the running string 103. Fluid pressure in the running string urges the conical portions 102a, b towards each other and forces the rollers 105 into contact with a wall 107 of a tubular member 110 sufficient to deform the wall of the tubing. Each roller 105 defines a circumferential rib 115 which provides a high pressure contact area. Following the creation of an expanded area 120 visible in FIG. 2, the fluid pressure in communication with the apparatus is let off, allowing the rollers 105 to retract. The apparatus 100 is then moved axially a predetermined distance to be re-energized and form another expanded area or is removed from the well. In the embodiment shown in FIGS. 1 and 2, the portions contacting the tube wall are rollers. However, the portions contacting the tubular wall could be non-rotating or could rotate in a longitudinal direction allowing the creation of a continued area of expansion within a tubular body.
There is a need therefore, for a slip and cone tool which requires less space as it is inserted into the well.
There is a further need for a slip and cone tool that requires less space after it has been set in the well.
There is a further need for downhole tools that utilize a removable expansion apparatus for activation.
There is a further need for a method of expanding a tubular wall in a well when the portion of the tubular to be expanded is located below a previously set, non collapsible tool.
There is a farther need for a downhole tool that can be operated or set in a wellbore by simple, remote means.
There is a further need for a downhole tool that can be operated or actuated without the use of chambers.
There is a further need for a downhole tool that can be operated without the use of gravity feed balls or other objects dropped from the earth's surface.